By Amelia Lucas | CNBC •Published August 8, 2019•Updated on August 8, 2019 at 4:27 pm

What to Know

Some vegans and vegetarians are saying they will not eat the meat-free burger because it is cooked on the same grill as chicken and beef.

Customers can request that their Impossible Whopper be cooked separately.

Vegans and vegetarians have cheered as more and more restaurants, from Subway to White Castle, add plant-based protein options from Beyond Meat and its rival Impossible Foods.

But as Burger King launches its meat-free Impossible Whopper nationwide Thursday, some vegans and vegetarians are hesitant to try it.

The controversy started last week when the chain’s U.S. head, Chris Finazzo, told Bloomberg the vegan burger would be cooked on the same broilers as chicken and beef. Some people who do not eat meat do not want their food to come into contact with meat at all during the cooking process.

A representative for Burger King, which is owned by Restaurant Brands International, said Thursday the chain has not changed how it plans to cook the burger.

Customers can request their Impossible Whopper be grilled on a different broiler than the meat. But vegans and vegetarians unaware of the option are now deciding if they want to try the Impossible Whopper.

One Twitter user warned that the burger is being cooked on the same grill as “the regular dead cow burger.”

Another pointed out that vegans still go to coffee shops, restaurants and grocery stores that serve nonvegan items.

Those who abstain from eating meat for religious reasons may follow more strict guidelines when it comes to cross-contamination with meat.

Cooking the Impossible Foods’ burgers, beef patties and chicken on the same grill makes it easier and more efficient for Burger King to offer the Impossible Whopper. The added complexity of a plant-based option is one reason keeping Burger King’s arch rival McDonald’s from offering a vegetarian-friendly burger. The Golden Arches has been trimming its menu to speed up service times — and customer satisfaction scores.

It is unlikely that the majority of customers buying the Impossible Whopper will even care that it is being cooked on the same grill. The growth in meat substitutes like the Impossible Burger is coming from flexitarians, a group of omnivores looking to cut down on their meat consumption. According to data from the NPD Group, 95% of plant-based burger buyers have also bought a beef burger within the last year.